Cameras typically used in known automotive imaging systems include an electronic image sensor, such as an active pixel sensor (APS) made using a complementary metal-oxide semiconductor (CMOS) process or a charge coupled device (CCD). This known electronic image sensor includes a plurality of light-sensitive pixels typically arranged in a matrix of rows and columns. FIG. 1A shows one example prior art electronic image sensor 12 including 144 pixels 12a arranged in a 12×12 matrix. In operation, circuitry of this known electronic image sensor converts light incident on a pixel into digital image data. A controller converts the image data into an image displayable on a display device.
To capture color data and enable creation of color images, these known electronic image sensors include a Bayer Color Filter Array (CFA). The Bayer CFA includes red, green, and blue color filters disposed or formed over the pixels (one per pixel) in a repeating pattern. FIG. 1B shows the prior art electronic image sensor 12 including a Bayer CFA including a repeating mosaic 13 of two green filters 13a, one red filter 13b, and one blue filter 13c. In operation, each colored filter only permits light of a particular wavelength (red, green, or blue in this case) to reach its pixel, which provides color information to the electronic image sensor. The controller uses a demosaicing algorithm to reconstruct the full-color image using this color information.
Since each color filter only permits light of particular wavelength to reach its pixel, about two-thirds less light reaches each filtered pixel than if that pixel was unfiltered. Use of a Bayer CFA—where each pixel is filtered—results in significantly reduced light sensitivity. This in turn results in a color image of inferior quality compared to a monochrome image obtained using an unfiltered electronic image sensor. This problem is exacerbated during use in low-light situations. For instance, the color image may have increased noise, aliasing, reduced spatial resolution, and reduced image sharpness caused by the reduced light sensitivity or the post-processing techniques used to account for the reduced light sensitivity.
There is a need for new automotive imaging systems that solve these problems.